The present invention relates to a method for producing a raster surface for use in the coloring of a contact lens.
Today, colored contact lenses are increasingly used as part of an elegant personal outfit with matched toning. As lenses are cheap and easy to use, they have become an essential part of a personal outfit.
A closer look at the iris of the eye reveals that the iris pattern has no geometrically regular forms. The patterning is unique to each person as fingerprints are, which means that there are no two people with identical irises. The iris patterns are radially arranged starting from the center of the pupil. The iris pattern contains elongated or oval shapes extending radially, flexuous, curved or substantially straight fibers and dots of varying size and irregular shape. The pupil may be encircled by a relatively irregular ring-like pattern, i.e. collarette, and in general the circumference of the iris looks darker than its inner areas. In the coloring of shapes and patterns, there is a soft variation in tones.
When the aim is to imitate natural iris patterns as closely as possible, efforts must be founded on the fact that, in order to achieve commercially remunerative products, it must be possible to manufacture them on an industrial scale by utilizing existing printing technology. The iris pattern of the eye mainly consists of such small details that it is technically impossible to print them so that the printed pattern looks photographically equivalent to the original. Traditional raster methods meet certain technical requirements in printing, such as the formation of tones and different colors and correct dosage of toner on the surface being printed. However, traditional dot raster patterns violate the forms of the iris of the eye. In addition, they produce in the iris a disturbing regular pattern that does not look natural.
As the raster technique is still the best method for the coloring of contact lenses as regards printing technology, a definite need has arisen to find a raster pattern that follows the organic patterning of the eye more faithfully than at present and to find a corresponding industrial method for implementing such a raster pattern.
The fundamental idea of the invention is that the raster to be used must follow or resemble the radial patterning of the natural iris. Moreover, the raster patterning must not contain recurrent or regular structures but continuous irregularity. Likewise, the distances between raster dots must vary within selected tolerance limits to meet the requirement of naturalness. In addition, as regards the technical requirements of printing, the raster dot must be sufficiently large to allow it to be printed e.g. on the surface of a contact lens or on a mould.
As for the features characteristic of the invention, reference is made to the claims.
In the method of the invention for producing a raster surface for use in the coloring of a contact lens, at first an image surface consisting of pixels, i.e. picture elements, is selected. The image surface selected may be a suitable surface of a gray tone, consisting of e.g. dots or squares of randomly varying shades. It is also possible to use a monochromatic image surface, i.e. a surface with black and white picture elements disposed at random. The surface as such can be technically implemented in several different ways, using different image processing programs, by artistic means, such as e.g. by spraying a surface with a coloring agent or by photographing a suitable sand surface, sand paper or even the noise pattern on a television screen.
In the method, a selected image surface is subjected to a tonal reduction operation, which means that a threshold tone value is defined for it and picture elements darker than the threshold are made black and picture elements lighter than the threshold are made white. This results in an image surface consisting of black and white picture elements, formed at random. After this, the black-and-white image surface is stretched radially in relation to a given point. The position of this stretching center corresponds to the center of the contact lens to be treated. The image surface, i.e. raster pattern thus obtained can be used with printing methods known in themselves to produce the raster pattern of a picture to be created on the contact lens.
The above description presents the minimum steps by which a raster surface used according to the invention can be produced. However, the image surface is preferably treated by various image processing methods to give the raster pattern the desired appearance. At different stages of the process, the image surface can be subjected to a softening treatment, which means that the image is magnified and then subjected to another tonal reduction treatment, thus giving the raster dots a more rounded shape and therefore a more natural appearance.
If the random image surface in the initial situation is a relatively light surface, then the image surface can be darkened by combining two or more identical image surfaces, i.e. by placing them one upon the other in positions somewhat displaced relative to each other in the direction of the plane of the image. In this way, a darker image surface preserving the stochastic disposition of pixels is produced.
Tonal reduction, softening and darkening operations can be repeated as appropriate until a black-and-white surface having the desired tonal value and consisting of different patterns disposed at varying distances from each other is achieved. However, the irregularly shaped patterns on such a surface with relatively uniform toning must be of a shape that allows them to be printed.
In experiments carried out, it was established that a relatively natural raster pattern is accomplished by stretching the image surface radially by 10-50%. A particularly good result is achieved when the stretching percentage is 15-35%.
The stretching can be performed linearly in a radial direction, but preferably the stretching is performed in a somewhat undulating fashion in the direction of the radius, thus producing a raster pattern looking as natural as possible. On the other hand, it is also possible to apply stretching in other directions as well, e.g. in a radial direction while at the same time rotating the image surface about the center.
By the method of the invention, it is possible to produce any patterns or images on a contact lens. To produce a contact lens iris pattern looking as natural as possible, the image to be created can be based on a picture of the iris of the eye produced manually or by a photographic or reproduction technique or by other methods and then applied to the contact lens by utilizing the raster technique. Another possibility is to build the image to be applied to the contact lens from components, in other words, the image is produced from differentiated pictures taken of different parts of the iris of the eye, produced manually or by a photographic or reproduction technique. Thus, the raster surface used to print the image may consist of e.g. a raster pattern of the iridial element, a raster pattern of the limbic ring and a raster pattern of the inner element, which, when printed one upon the other, form the raster surface to be used.
An advantage provided by the method of the invention as compared with prior-art techniques is above all a natural appearance of the final result. The method of the invention allows industrial and economic production of natural-looking contact lenses, which, in the methods for coloring contact lenses known so far, has only been a distant goal.